Abstract As proved by 29 Si and 15 N NMR spectra, the reaction of N, O-bis (trimethylsilyl) hydroxylamine with diketene yields a mixture of E and Z isomers of O, O'-bis (trimethylsilyl) acetoacetohydroximic acid ((E)-3 and (Z)-3), and not the conformers of N, O-bis (trimethylsilyl) acetoacetohydroxamic acid (1), as believed up to now. In contrast, the acetylation of N, O-dimethylhydroxylamine leads to methyl N-methylacetohydroxamate (5), ...
